Дата: 31.10.2023 г., 14:00 ч. Място: Зала 403, ИМИ - БАН Докладчик: Петър Далаков, ИМИ - БАН Курс: Introduction to Projective Structures and Opers Резюме: A complex projective structure on a Riemann surface is determined by an atlas, whose transition functions are Moebius (fractional-linear) transformations. There are multiple   descriptions of these structures: as certain flat PGL_2-bundles, as Sturm-Liouville operators, as holomorphic connections on the (first) jet bundle of the dual of a theta-characteristic, etc. This mini-course is an introduction to the fundamentals of projective structures, accessible to students and non-specialists. We will also explore links to some classical geometric objects (such as quadratic differentials and Schwarzian derivatives), as well as some generalisations (G-opers) introduced by Beilinson and Drinfeld. https://icms.bg/introduction-to-projective-structures-and-opers/    

На 31 октомври 2023 г. (вторник) от 16:00 часа в зала 578 на ИМИ-БАН ще се проведе заседание на семинара на секция „Математически основи на информатиката". Доклад ще изнесе д-р Константин Воробьов (ИМИ - БАН). Абстракт. In this work, we consider the problem of determining the exact value of A_2(n, {d, d+2}) defined as the maximal cardinality of a binary code of length n with two possible distances d and d+2 . We prove that for fixed even d and n big enough, an optimal code must be a constant-weight code of weight d/2+1 with possibly no more than one additional codeword of a different weight. We also find exact values A_2(n, {4, 6}) and A_2(n, {6, 8}) [...]